1. Field of the Invention
The present invention relates to a mobile communication system that includes a mobile switching center having a multiprocessor configuration and at least one radio base station subordinate to the mobile switching center.
2. Description of the Related Art
Referring to FIG. 12, an exemplary configuration is shown of such a mobile communication system that includes a mobile switching center having a multiprocessor configuration and a plurality of radio base stations subordinate to the mobile switching center.
In the shown example, a system S1 comprises a mobile switching center MSC that includes a plurality of processors CPR1 to CPRn, and a plurality of radio base stations BSC1 to BSC5 subordinate to the processors.
The processors CPR1 to CPRn of FIG. 12 example are subjected to an integrated control by a main processor MPR. The radio base stations BSC1 and BSC2 are allocated to the processor CPR1, with the radio base stations BSC3 and BSC4 allocated to the processor CPR2. Location areas LAC1 to LAC3 are subordinate correspondingly to the radio base stations BSC1 to BSC5.
In FIG. 12, the processors CPR1 to CPRn are linked to another system S2.
In another configuration shown in FIG. 13, a single radio base station BSC connects with mutually independent signaling links from the respective processors CPR1, CPR2, etc.
One goal of the configurations of FIGS. 12 and 13 is to improve the reliability. The FIG. 13 configuration in particular may often be employed in cases where the radio base station BSC does not balance with the mobile switching center MSC in respect of subscriber capacities and throughputs.
In a relationship between the mobile switching center MSC and the radio base station BSC that have a system specification of FIG. 13 configuration, a small subscriber capacity of system configuration provides the ratio of 1:1 or 2:1 in the corresponding relation between the processors CPR of the mobile switching center MSC and the radio base station BSC as in exemplary configurations of FIGS. 14 and 15, whereas a large subscriber capacity of system configuration provides the ratio of multitude: multitude in the corresponding relation between the processors CPR and the radio base stations BSC as shown in FIG. 16.
In such a mobile communication system S1, consideration is given to the case where a call from a subscriber of the other system S2 or of that system S1 is received by a mobile subscriber MS under the system S1.
Although the termination call is controlled at that time, the processor CPR having a control program MCA for controlling that call is a processor that takes charge of call originating control in case of the call under its own system, but it is a processor that has received the call control information in case of an incoming connection call from the other system.
By means of a signaling connection control part (SCCP) that corresponds to the third layer in the function level of No. 7 signaling system, the processor CPR sends a mobile subscriber MS call demand signal PAGE to the radio base station BSC. Used herein is a connectionless signal from the SCCP.
The radio base station BSC then calls the mobile MS and returns a call response signal PAGE_RSP responding thereto to the mobile switching center MSC. Used herein is a connection oriented signal from the SCCP.
Such a prior art may allow the destination of return of the call response signal PAGE_RSP to result in the processor other than the processor CPR in which the termination call is controlled.
More specifically, in the exemplary configuration of FIG. 17 shown in a manner corresponding to FIGS. 15 and 16, when the processor CPR1 sends a call demand signal PAGE to the radio base station BSC1, a call response signal PAGE_RSP responding thereto may possibly be returned to the processor CPR2.
Referring to FIG. 17, the processor CPR in the layer configuration includes an incoming call control part ICA, a moving call control part MCA and a moving protocol control part MPC. The processor interface part F1 has the functions of the SCCP, signaling network level MPT and level 2 in the No. 7 signaling system.
The radio base station BSC has an interface part equivalent to the processor interface part F1 and has a base station call control part BCA and a radio call control part RCA.
In the event that the call response signal PAGE_RSP has been returned to the processor CPR2 different from the processor CPR1 that sent the call demand signal PAGE as described above, all the subsequent call control signals required have to be transferred between the processor CPR1 and the processor CPR2.
The reason is that the call response signal PAGE_RSP sent form the radio base station BSC1 is a connection request message (connection establishing demand) of the SCCP connection oriented signal and that to ensure the sequence of the subsequent sending data the same SLS (signaling link selection) value is used to provide a control such that sending is made to the same signaling link.
This often resulted in an increase in the amount of resources (the amount of memory block, processor activity ratio, etc.) for use in the interprocessor communication, as compared with the case where the call response signal PAGE_RSP has been returned to the same processor CPR.
In order to transfer data signals from the processor CPR2 to the processor CPR1, as shown in FIGS. 18A and 18B the call response signal PAGE_RSP (FIG. 18B) is arranged to include the CPR number within the call ID information TAG contained in the call demand signal PAGE (FIG. 18A).
Alternatively, use may be made of a mobile identifier IMSI contained in the call response signal PAGE_RSP to search the subscriber data base being managed in the main processor MPR. Otherwise, for the signals following the call response signal PAGE_RSP, a local reference number including the processor CPR number may be placed in a CC message returned from the mobile switching center MSC whereby the local reference number can automatically be inserted into the subsequent signals sent from the radio base station BSC.
The processor number can thus be readily identified for transfer. The transfer may be effected by way of the SCCP layer or the call control (application).
In any case, however, an increase will be inevitable in the amount of resources for use in the interprocessor communication.
It is therefore the object of the present invention to provide a signaling link selection method and apparatus in which the destination of return of a call response signal PAGE_RSP is arranged to result in a processor CPR having controlled termination calls thereby preventing any increase in the amount of resources (the amount of memory block, processor activity ratio, processor-to-processor adapter activity ratio) for use in the interprocessor communication.
According to a first aspect of the present invention, in order to achieve the above object, a mobile communication system includes a mobile switching center having a multiprocessor configuration and at least one radio base station subordinate to the mobile switching center, with a single radio base station being connected with signaling links independent of a plurality of processors within the mobile switching center.
Then, when a call issued from the or other system is received by a subscriber under the system, call ID information contained in a mobile call demand signal sent from the mobile switching center to the radio base station has a storage area for an identifier of a processor within the mobile switching center, and the radio base station allows the destination of return of a mobile call response signal to be the processor indicated by the processor identifier.
Preferably, in case no processor identifier is stored in the mobile switching center processor identifier storage area of the call ID information contained in the mobile call demand signal, the radio base station selects at random a signaling link to return the mobile call response signal.
It is more preferable that in case a called subscriber class has a priority, the processor identifier storage area store an ID number of a processor in which a termination call is under control at all times.
Preferably, in case a calling subscriber class has a priority, the processor identifier storage area stores an ID number of a processor in which a termination call is under control at all times.
According to a second aspect of the present invention there is provided a mobile communication system that includes a mobile switching center having a multiprocessor configuration and at least one radio base station subordinate to the mobile switching center, with a single radio base station being connected with signaling links independent of a plurality of processors within the mobile switching center, wherein when a call issued from the or other system is received by a subscriber under the system, call ID information contained in a mobile call demand signal sent from the mobile switching center to the radio base station has a storage area for a signaling link number between the mobile switching center and the radio base station, and wherein the radio base station allows the destination of return of a mobile call response signal to be the signaling link indicated by the signaling link number.
Preferably, in such a configuration, providing that no signaling link number between the mobile switching center and the radio base station is stored in the call ID information contained in the mobile call demand signal, the radio base station selects at random a signaling link to return the mobile call response signal.
It is more preferable that when the radio base station determines a link number to return the mobile call response signal from a processor ID number, a certain law be imparted so that a load between signaling links can be shared of a series of subsequent signals from the radio base station.
Furthermore, preferably, in case, with a signaling link independent of the processors within the mobile switching center being connected with a second radio base station different from a first radio base station, the mobile call demand signal is sent to the second radio base station in addition to the first radio base station when it is received by a subscriber under a first system, no processor identifier is stored in the processor identifier storage area of the call ID information contained in the mobile call demand signal sent to the second radio base station so that the second radio base station can select at random a signaling link to return the mobile call response signal.
Furthermore, preferably, in case, with a signaling link independent of the processors within the mobile switching center being connected with a second radio base station different from a first radio base station, the mobile call demand signal is sent to the second radio base station in addition to the first radio base station when it is received by a subscriber under a first system, no signaling link number is stored in the mobile switching center to radio base station link number storage area of the call ID information contained in the mobile call demand signal sent to the second radio base station so that the second radio base station can select at random a signaling link to return the mobile call response signal.